NaN fuzzing improvements (#1913)

* make DE_NAN avoid creating nan literals in the first place
* add a reducer option `--denan` to not introduce nans in destructive reduction
* add a `Literal::isNaN()` method
* also remove the default exception logging from the fuzzer js glue, which is a source of non-useful VM differences (like nan nondeterminism)
* added an option `--no-fuzz-nans` to make it easy to avoid nans when fuzzing (without hacking the source and recompiling).

Background: trying to get fuzzing on jsc working despite this open issue: https://bugs.webkit.org/show_bug.cgi?id=175691

1 files changed, 7 insertions, 1 deletions

diff --git a/src/tools/wasm-opt.cpp b/src/tools/wasm-opt.cpp
index 61e554276..d2f3d718c 100644
--- a/src/tools/wasm-opt.cpp
+++ b/src/tools/wasm-opt.cpp
@@ -71,6 +71,7 @@ int main(int argc, const char* argv[]) {
   std::string extraFuzzCommand;
   bool translateToFuzz = false;
   bool fuzzPasses = false;
+  bool fuzzNaNs = true;
   std::string emitJSWrapper;
   std::string emitSpecWrapper;
   std::string inputSourceMapFilename;
@@ -112,6 +113,9 @@ int main(int argc, const char* argv[]) {
       .add("--fuzz-passes", "-fp", "Pick a random set of passes to run, useful for fuzzing. this depends on translate-to-fuzz (it picks the passes from the input)",
            Options::Arguments::Zero,
            [&](Options *o, const std::string& arguments) { fuzzPasses = true; })
+      .add("--no-fuzz-nans", "", "don't emit NaNs when fuzzing, and remove them at runtime as well (helps avoid nondeterminism between VMs)",
+           Options::Arguments::Zero,
+           [&](Options *o, const std::string& arguments) { fuzzNaNs = false; })
       .add("--emit-js-wrapper", "-ejw", "Emit a JavaScript wrapper file that can run the wasm with some test values, useful for fuzzing",
            Options::Arguments::One,
            [&](Options *o, const std::string& arguments) { emitJSWrapper = arguments; })
@@ -166,7 +170,9 @@ int main(int argc, const char* argv[]) {
     if (fuzzPasses) {
       reader.pickPasses(options);
     }
-    reader.build(options.getFeatures());
+    reader.setFeatures(options.getFeatures());
+    reader.setAllowNaNs(fuzzNaNs);
+    reader.build();
     if (options.passOptions.validate) {
       if (!WasmValidator().validate(wasm, options.getFeatures())) {
         WasmPrinter::printModule(&wasm);